How can I get audio attachment download link from a post?

Dear All,
Please help me out about how to get attachment download link of first audio attachment of a WordPress post. I spent huge time after this single problem.
Here is my code:

$post=get_post($postID);
if( $posts ) :
foreach( $posts as $post ) : setup_postdata( $post );?>
 <div class="download_box fix">
      <?php  $args = array(
            'post_type' => 'attachment',
            'numberposts' => -1,
            'post_status' => null,
            'post_parent' => $postID
           );
            $attachments = get_posts($args); ?>
            <?php $attchID=$attachments[0]->ID; ?>
            <a href="<?php echo wp_get_attachment_url( $attchID );?>">Download</a>
        </div>
        <?php endforeach; ?>
        <?php endif; ?>

The above code is returning a link of the post itself.
Can anyone tell me if I missed something? Please help me out.

Thank you